Despite technological advances in surgery and radiotherapy for patients who suffer from oral squamous cell carcinoma (OSCC), the survival rate has remained un-improved during the last two decades indicating our ability to treat patients has reached a plateau. We have reported that proteasome inhibition induced ER stress and C/EBP-homologous protein- (CHOP) mediated apoptosis in a variety of HNSCC cell lines, including several that are not sensitive to cisplatin. ER stress leads to a physiological response known as the unfolded protein response (UPR) which consists of distinct parallel genetic programs that attempt to restore homeostatic protein folding or lead to apoptosis if the stress is prolonged or robust. We hypothesized that we could use high throughput screening (HTS) with large diverse chemical libraries to identify novel small molecule activators CHOP to induce apoptosis in OSCC cells. We have developed a complementary cellbased assay using stably transfected CHO-K1 cells that individually report on the PERK/elF2o/CHOP (apoptotic) and the IRE1/XBP1 (adaptive) pathways of the UPR. Identifying compounds that specifically activate only PERK/elF2a/CHOP and not IRE1/XBP1 has allowed us to rule out many compounds that are generally toxic as well as those that alter general properties of protein synthesis and/or folding, such as Ca2+ or redox status. 65 "hit" compounds have been identified that robustly activated the CHOP but not the XBP1 reporter with chemical signatures amenable for synthetic analoging and pharmaceutical development. We propose to test the ability of these 65 compounds along with commercially available analog series to induce CHOP expression and apoptosis in a panel of OSCC cells. The most promising candidates will be evaluated in vivo in a well-characterized rodent xenograft model. The long-term objectives of the proposed studies are to elucidate the ability of these novel small molecules to induce CHOP and inhibit growth or induce apoptosis in OSCC cells and to further screen very large diverse libraries of chemical probes with our complementary cell-based screen. Small molecule UPR agonisits identified through these studies will provide a convenient cost-effective means of treating patients suffering from a disease for which therapies are limited to minimally effective chemotherapies, damaging radiation or painful surgeries that often interfere with their ability to speak, chew or even breathe. PUBLIC HEALTH RELEVANCE: The survival rate for patients with tumors in the head and neck region has not improved in over 20 years. We screened a chemical library of 66,000 small molecules to identify novel drug-like compounds. The proposed studies will determine the ability of "hits" from this screen to interfere with the growth of or kill head and neck tumor cells.